The invention relates to adjusting an input signal level of a Sigma-Delta converter. A control signal indicative of an input signal level to said Sigma-Delta converter is generated, and the input signal level to said Sigma-Delta converter is adjusted in dependence of said control signal. The control signal is generated as a signal indicating an operating condition of said Sigma-Delta converter. In this way, internal signals from the Sigma-Delta converter can be used to determine the state of the Sigma-Delta converter, i.e. whether it is operating within its operational input range or not, and whether it is close to the limits of the operational input range. This provides a simple, but accurate guidance of an automatic gain control upstream of the Sigma-Delta converter.